GRAFT COPOLYMERIZATION OF ACRYLAMIDE ONTO POLYPROPYLENE FILMS BY PLASMA TECHNIQUE

The graft copolymerization of acrylamide onto polypropylene (PP) Film was carried out by using a capacitively coupled rf plasma apparatus with external plate electrodes. The relationship between the surface structure of the Ar plasma-treated PP films and the extent of grafting of acrylamide on the films was studied through observing the effects of discharge power and exposure time on the relative content of free-radical on the film surface. Meanwhile, the wettability and surface energy of the PP film were measured.     

Surface roughness and hydrophilicity enhancement of polyolefin‐based membranes by three kinds of plasma methods

The introduction of antibacterial property, conductivity, wettability and antithrombogenicity into polyolefin‐based membranes has evoked much attention, which can be achieved by coating hydrophilic polymers. Therefore, it is necessary to modify the roughness and hydrophilicity of polyolefin‐based membranes to enhance the coating ability. In this paper, three kinds of plasma methods, including inductively coupled (ICP) plasma, radio frequency low pressure (RFP) plasma and atmospheric dielectric barrier discharge (DBD) plasma, were used to modify the surface of the polyethylene (PE), polypropylene (PP) and polyester‐polypropylene (PET–PP) membranes. The surface roughness of the plasma‐modified PE, PP and PET–PP films was investigated by scanning electron microscopy (SEM) and atomic force microscope (AFM). The polar functional groups of films were observed by energy dispersive spectrometer (EDX) and X‐ray photoelectron spectroscopy (XPS). Besides, the hydrophilicity of the plasma‐modified PE, PP and PET–PP films was evaluated by water contact angle measurement. It was found that the surface roughness and hydrophilicity of plasma‐modified PE, PP and PET–PP films increased with the generation of oxygen‐containing functional groups (i.e. C―O, and C?O). The PET–PP membranes were treated by RFP plasma at different processing powers and times. These results indicated that plasma is an effective way to modify films, and the treatment time and power of plasma had a certain accumulation effect on the membranes' hydrophilicity. As for the roughness and hydrophilicity, the DBD plasma modifies the PE film, which is the optimum way to get the ideal roughness and hydrophilicity. Copyright © 2015 John Wiley & Sons, Ltd.     

Plasma modification of polypropylene surfaces and grafting copolymerization of styrene onto polypropylene

The surface of polypropylene(iPP) is modified with glow discharge plasma of Ar,so that the modified surfaces of iPP films are obtained.The studies of scanning electron microscopy(SEM) show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FTIR) spectroscopy.The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated.The free radical of modification surfaces of iPP is measured by chemical method.The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene(St) in St.The grafting polymer of St onto iPP is characterized by FTIR.The grafting rate is dependent on plasma exposure time and discharge voltage.The studies show that homopolymerization of St is undergone at the same time during the grafting-copolymerization of St onto iPP.     

Grafting of glycidyl methacrylate onto polypropylene using supercritical carbon dioxide

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO₂) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO₂ at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO₂, film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.     

Preparation and enhanced properties of poly(propylene)/ silica‐grafted‐hyperbranched polyester nanocomposites

A series of poly(propylene) silica‐grafted‐hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn? H20), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface of SiO₂ particles (30 nm) through 3‐glycidoxy‐propyltrimethoxysilane (GPTS) was prepared. The effect of silica‐grafted‐modified Boltorn? H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn? H20 was successfully grafted onto the SiO₂ surface confirmed by FT‐IR and X‐ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica‐grafted‐modified Boltorn? H20 (3–5 wt% SiO₂) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica‐grafted‐modified Boltorn? H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica‐grafted‐modified Boltorn? H20 particles were added compared with PP/SiO₂ or PP/SiO₂‐GPTS composites. Copyright © 2004 John Wiley & Sons, Ltd.     

Adsorption behavior of urokinase by polypropylene film modified with amino acids as affinity groups

In order to prepare a new-type adsorbent with an affinity ligand, polypropylene films modified with amino acid groups such as -phenylalanine (Phe), , -Phe, -cysteine (Cys), and , -tryptophane (Try), were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films and subsequent amination of poly-GMA graft chains. The physical and chemical properties of the GMA-grafted PP film and the PP film modified with amino acid groups were investigated by IR and XPS. The adsorption of urokinase for the PP films modified with four kinds of amino acid groups were examined under various conditions, such as the contents of the amino acid group and pH value. The adsorption of urokinase increased with the increasing content of the amino acid group. The adsorption of the PP film modified with four kinds of amino acid groups was in the following order: -Phe> , -Phe> , -Try> -Cys. The adsorption amounts of urokinase by the PP film modified with four kinds of amino acid groups at pH 7.4 was higher than that at pH 9.0.     

Manipulating the surface properties of polyacrylamide with nitrogen plasma

Polyacrylamide (PAL) was physically adsorbed onto a hydroxylated silicon surface to form a uniform PAL film and the up-top PAL thin film was treated by nitrogen (N₂) plasma for surface modification. The atomic composition of the modified surface of the PAL film adsorbed on silicon substrate was analyzed with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The surface energy of PAL film was calculated from the data of contact angle of three-probe liquid. The FTIR results show an increase of peak intensity at 1214 cm⁻¹ (NH₂ stretch vibration) after the nitrogen plasma treatment, which confirms that the nitrogen was grafted to the PAL surface in the process of N₂-plasma treatment. The XPS results show that the ratio of relative intensity of N1s to O1s increases with increasing the plasma treatment time, which further affirms the formation of the amine groups on the PAL surface after the nitrogen plasma treatment. The surface tension increases with increasing the plasma grafting time. However, the surface energy decreases rapidly at the early stage when stored in air and approaches to an equilibrium value. It suggests that some physically-adsorbed ions and alkyl radicals on PAL surface can rapidly lose their activities. The increase of the surface tension of the plasma treated PLA films is due to the amine groups covalently grafted to PAL surface.     

Excellent anti‐bacterial activity and surface properties of polyamide‐6 films modified with argon‐plasma and methyl diallyl ammonium salt‐graft

In this study, the effect of argon‐plasma treatment on the grafting of methyl diallyl ammonium salt (MDAA) onto polyamide‐6 film and the anti‐bacterial and surface properties of the plasma‐ and graft‐treated film were investigated. The grafting amounts of MDAA caused by argon‐plasma treatment increased with the increase in the plasma exposure time and plasma power. The analyses of Fourier transform infrared (FT‐IR) spectroscopy and electron spectroscopy for chemical analysis (ESCA) spectra revealed that the epoxy and vinyl groups of MDAA could be grafted on the argon‐plasma treated polyamide‐6 film. The survey spectra of ESCA, the patterns of atomic force microscopy (AFM), and the spectra from scanning electron microscopy (SEM) were employed to certify the surface modification of argon‐plasma treated and the argon‐plasma treated/MDAA grafted polyamide‐6 films. Argon‐plasma treatment could generate the functional group and increase the roughness on the surface of polyamide‐6 film. This phenomenon could enhance the grafting effect of MDAA. The anti‐bacterial property of argon‐plasma treated/MDAA grafted polyamide‐6 film was excellent. This argon‐plasma treated/MDAA grafted polyamide‐6 film was expected to be applied on the field of packing. Copyright © 2008 John Wiley & Sons, Ltd.     

Adhesion Enhancement and Characterization of Plasma Polymerized 1,2-Dichloroethane on Polypropylene Surface

Polypropylene (PP) films were modified in 1,2-dichloroethane (DCE) plasma. Surface energy measurement and rate of deposition showed two-step surface modification. First, incorporation of chloride ions on PP surface followed by deposition of cross-linked layer. DCE plasma modified PP films were subsequently compared with earlier reported work on carbontetrachloride (CCl₄) and chloroform (CHCl₃) plasma modification. Modified films were characterized using ATR-FTIR technique by monitoring the relative changes in intensities of C–H stretch vibrations. The nature of deposition on PP film was characterized using FTIR technique and solubility test. Peel strength measurements of DCE, CCl₄, and CHCl₃ plasma modified films showed improvement in bonding strength. Durability of plasma modified PP film was studied by calculating surface energy and peel strength of samples aged for two months.     

原位固相接枝改性碳酸钙/聚丙烯复合材料的制备

用马来酸酐（MAH）在碳酸钙（CaCO3）表面引入双键,通过原位固相接枝法将聚丙烯蜡（PPW）化学键合在CaCO3表面,制得3种接枝率的CaCO3-MAH-PPW。 将这3种改性CaCO3填充聚丙烯（PP）制备复合材料,研究了PP/CaCO3界面作用对复合材料强度的影响。 结果表明,CaCO3表面经PPW接枝改性后在PP中的分散性提高,与PP相容性变好;随着改性CaCO3表面PPW接枝率的提高,CaCO3与PP之间界面作用逐渐增强。 当PPW接枝率为4.48 mg PPW/g CaCO3时,CaCO3与PP之间的界面作用最强,复合材料拉伸强度下降最小,杨氏模量提升最大,当m(PP)∶m(CaCO3)=100∶50时,杨氏模量达0.86 GPa,是纯PP的1.63倍;而PPW化学接枝率为2.49 mg PPW/g CaCO3时,CaCO3与PP之间的界面作用适中,复合材料缺口冲击强度提升最大,且当m(PP)∶m(CaCO3)=100∶10时,缺口冲击强度达3.91 kJ/m2,是纯PP的1.35倍。     

γ-Ray-induced grafting of DMAEMA and AAc onto PP by two step method

Binary graft copolymerization of thermosensitive 2-(dimethylamino) ethyl methacrylate (DMAEMA) and pH sensitive acrylic acid (AAc) monomers onto polypropylene (PP) films was carried out by a two step method using a ⁶⁰Co gamma radiation source. The PP film was initially modified by grafting of DMAEMA through a direct method. The DMAEMA-g-PP film obtained was then subjected to radiation grafting of AAc by the pre-irradiation method to give (DMAEMA-g-PP)-g-AAc. The optimal conditions, such as reaction time, reaction temperature, monomer concentration, and dose were studied. The grafted samples were verified by the FTIR-ATR spectroscopy and swelling; thermal properties were analyzed by DSC and TGA.     

Surface Modification and Characterization of Dichloromethane Plasma Treated Polypropylene Film

Surface of polypropylene (PP) film was modified in plasma of dichloromethane (CH₂Cl₂). The nature of surface modifications and formation of cross-linked layer due to plasma polymerization was studied by surface energy measurements and solubility test. Surface modification achieved by CH₂Cl₂ plasma was compared with the reported work on chloroform (CHCl₃) and carbontetrachloride (CCl₄) plasma modifications. Modified surface characterized by ATR-FTIR technique indicated formation of saturated and unsaturated cross-linked product. On the basis of relative intensity change of the specific bands, the site of attachment of chlorine on PP surface was investigated. Adhesive strength of modified film was measured by T-peel test method. Stability of modified surface was studied by measuring surface energy and peel strength after two months.     

Plasma brominated polymer particles as grafting substrate for thiol‐terminated telomers

A combined surface activation and “grafting to” strategy was developed to convert divinylbenzene particles into weak cation exchangers suitable for protein separation. The initial activation step was based on plasma modification with bromoform, which rendered the particles amenable to further reaction with nucleophiles by introducing Br to a surface content of 11.2 atom‐%, as determined by X‐ray photoelectron spectroscopy. Grafting of thiol‐terminated glydicyl methacrylate telomers to freshly plasma activated surfaces was accomplished without the use of added initiator, and the grafting was verified both by reduction in bromine content and the appearance of sulfur‐carbon linkages, showing that the surface grafts were covalently bonded. Following grafting the attached glydicyl methacrylate telomer tentacles were further modified by a two‐step procedure involving hydrolysis to 2,3‐hydroxypropyl groups and conversion of hydroxyl groups to carboxylate functionality by succinic anhydride. The final material was capable of baseline separating four model proteins in 3 min by gradient cation exchange chromatography in a fully aqueous eluent.     

Surface modification of plasma‐pretreated expanded poly (tetrafluroethylene) films by graft copolymerization

A two‐step process based on a low‐pressure helium plasma treatment followed by acrylic acid‐grafting copolymerization was used for the surface modification of expanded polytetrafluoroethylene (ePTFE) films. The effects of plasma treatment power and treatment time on the hydrophilicity of the film surface were investigated. The wettability of the ePTFE film surface was characterized by water contact angle, and the surface compositions of the untreated and treated ePTFE samples were evaluated by atomic force microscopy and XPS. Contact angle measurements revealed that the hydrophilicity of the ePTFE film surface was greatly enhanced by the combined actions of the plasma treatment and acrylic acid grafting, and the contact angle decreased from 145° to 66°. Atomic force microscopy analyses showed that the surface roughness increased after the plasma treatment. XPS analyses showed substantial increase in the concentration of carbon and oxygen atoms and a decrease in the concentration of fluorine atoms at the film surface. T‐peel strength showed an improved bonding strength between the film and an adhesive tape after the treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Conductive thin film formation onto radiation grafted polymeric surfaces using electroless plating technique

Surface modification of polypropylene films (PP) was carried out via radiation induced graft copolymerization of 4‐vinyl pyridine (4VP) and acrylamide (AAm) to enhance the adhesion ability of the PP surface for electroless deposition of copper. Factors affecting the grafting process such as suitable solvent, comonomer composition and concentration and irradiation dose were optimized. The grafted films produced were characterized by studying their Fourier‐transform infrared (FTIR) spectra and thermal stability. The grafted films were copper‐plated by electroless deposition using Pd as the catalyst to initiate the redox reaction. The influence of catalytic activation method parameters on the plating rate were studied. Scanning electron microscopy revealed a dense and void‐free copper deposited film. The adhesion of the deposited copper film to the modified PP films was determined by measuring the tensile strength of the copper plated films. The electrical characteristics of the copper plated films in comparison with grafted films were studied. The results showed the high adhesion of the deposited copper film to the grafted PP film as well as the high electrical conductivity. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of the surface characteristics of polypropylene films treated by Ar and mixed gas (Ar/O2) atmospheric pressure plasma

In an attempt to modify the hydrophobic surface properties of polypropylene (PP) films, this study examined the optimum process parameters of atmospheric pressure plasma (APP) using Ar gas. Under optimized conditions, the effects of a mixed gas (Ar/O2) plasma treatment on the surface-free energy of a PP film were investigated as a function of the O2 content. The polar contribution of the surface-free energy of the PP film increased with increasing O2 content in the gas mixture. However, slightly more oxygen-containing polar functional groups such as CO, CO, and COO were introduced on the PP film surface by the Ar gas only rather than by the Ar/O2 gas mixture. In addition, AFM analysis showed that the Ar plasma treatment of the PP film produced the smoothest surface as a result of the relatively homogeneous etching process.     

Influence of Plasma Treatment on the Electroless Deposition of Copper on Carbon Fibers

Air and nitrogen glow discharge were used to replace chromic acid pretreatment to deposit copper film on carbon fiber surfaces from an CuSO₄‐HCHO electroless system. A greater copper uptake and a more uniformly coated copper film were obtained for plasma‐treated carbon fibers. The adhesion between the copper film and the carbon fibers was also improved. An orthogonal table L₉(3⁴) was used to study the effects of discharge pressure, discharge power, time and gas type on the copper uptake. Scanning electron microscopy (SEM), reflection absorption infrared spectroscopy (RAIR) and X‐ray photoelectron spectroscopy (XPS) at different depths were applied to characterize the physical and chemical changes of the surface of the carbon fibers. The results showed that after plasma treatment, the carbon fiber surface became rough and several types of polar oxygen groups, such as carboxylic acid COOH, esters COOC, quinones Ph?O, etc., were introduced into the carbon fiber surface. A mechanism of plasma treatment effects on copper electroless deposition on the carbon fiber surface is also suggested.     

Surface and bulk modification of polyolefins by functional aryl nitrenes as highly reactive intermediates

Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV‐irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene‐propylene and ethylene‐octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene‐propylene‐copolymers, less than half of it to ethylene‐octene‐copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers.     

Sorption of ethanesulfonic acid by nylon-6 containing various numbers of end groups

From the analysis of the permeation of ³⁵S labeled ethanesulfonic acid, through nylon-6 films sorption isotherms were obtained. The films are characterized by their largely different content of carboxyl and amino end groups. It was found that the shape of the isotherm depends on the molar ratio of the two end groups: an S-shape curve for the film containing the carboxyl end group larger than the amino end group and a Langmuir-type curve for the film containing comparable numbers of end groups. These results were explained by the McGregor-Harris theory in which the acid dissociation constants of the two end groups in nylon were estimated experimentally.     

Covalently attached graft polymer monolayer on organic polymeric substrate via confined surface inhibition reaction

A grafting technique was proposed for the preparation of polymer monolayer on polymeric substrate. On the basis of our recent work on polymer‐supported inhibitor (PSI), hydroquinone (HQ) was first implanted onto polypropylene (PP) surface through UV‐initiated grafting. The resulting immobilized HQ was used as PSI for the thermal‐induced free radical polymerization (FRP) of acrylic acid (AA). The inhibition mechanism was similar to that of free HQ molecule, that is, polymer chain‐carrying radical or peroxy radical could be deactivated by abstracting hydrogen atom from hydroxyl group of immobilized HQ, and the resulting oxyradical (semiquinone radical) combined with another active chain free radical. According to this mechanism, a devised redox initiator consisting of sodium hydrogen sulfite and ammonium persulfate was used to initiate FRP of AA in water at low temperature (50 °C). High crystalline biaxial oriented PP film with HQ immobilized was deliberately laid in this system as a radical trap to capture poly(acrylic acid) (PAA) short chain radical. Through X‐ray photoelectron spectra (XPS) analysis it was found that the atom ratio of C_HQ (carbon in HQ) to C_COOH (carbon in COOH) decreased with prolonging polymerization time and became stable after about 30 min. The formed PAA short chain on the surface showed a distribution of monolayer, and the saturated thickness was calculated as 5–7 Å. The degree of polymerization of graft chain in PAA monolayer was estimated as 15–20 through three different models. Relating to surface coverage being 100% in ideal densely packed PAA monolayer, real monolayer surface coverage in such reaction system was estimated as 12.3–18.5%. This method was expected to give us a general approach for constructing kinds of graft polymer monolayer on polymeric substrate, because the involved chemistry was only common inhibition reaction between immobilized inhibitor (HQ) and FRP system in solution (herein redox initiating system of AA). We named this grafting chemistry as confined surface inhibition reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 745–755, 2007